Update README.md

Author: Patrick Maynard

README.md

@@ -29,7 +29,7 @@ https://symfony.com/doc/current/templating/twig_extension.html#register-an-exten
 Once that's done, you can use the new function in Twig files like this:
 
 ```
-{{ trace() }}
+{{ trace()|raw }}
 ```
 
 UNTESTED: You could also try using `{{ trace_via_debug_backtrace() }}` to get different formatting. I haven't yet tested this.